1. Field of the Invention
This invention relates to conditioning gases used to inflate body cavities prior to and during medical procedures. More specifically, it relates to a compact device for, and method of, heating, humidifying and filtering insulation and other gases.
2. Related Art
From the beginning of laparoscopic surgical procedures some thirty years ago, it has been assumed that the condition of gases used to inflate body cavities and spaces were physiologically and pathologically benign. While the importance and use of temperature and moisture conditioning of anesthesia gases has been well known, until recently little attention had been given to the particulate, temperature and/or humidity condition of insufflation gases used to create a pneumoperitoneum. Reduction in core body temperature, introduction of foreign bodies and drying of surfaces (including peritoneal surfaces), resulting from the introduction of insufflation gases in such surgical procedures are continuing problems.
A commonly used insufflation gas is carbon dioxide which is typically provided as a liquid in compressed gas cylinders. The pressure in these cylinders, when at equilibrium with ambient environment of 20.degree. C., is 57 atmospheres (5740 kPa). The carbon dioxide gas is typically provided to the surgical site at a pressure of 15 mmHg via an adjustable, throttling pressure regulator and flow controller called an insufflator. Many models of insufflators are available such as the Storz Model 26012 (Karl Storz Endoscopy-America Inc., Culver City, Calif.). In general, insufflators do not filter, few have the capability to control the gas temperature, and none are known to have the capability of humidifying the gas.
It is known to filter insufflation gas to prevent inorganic particles such as metallic fillings or particles, rust, dust, and polymer particles from passing into the pneumoperitoneum (see, e.g., Ott, D.E., J Gynecol. Surg., 5:205-208 (1989)). The location and type of filter, however, are very important factors which will influence the effectiveness of the method. Filters having a pore size as small as 0.2 microns have been used in previous insufflation systems. These devices, however, utilize a filter material that is typically hydrophilic and when it becomes moist, loses its strength and some of its filtering effectiveness. Moreover, because these prior art filter devices are not hydrophobic, they lose their filtering capability by tearing under the water pressure caused by accidentally suctioning or syphoning peritoneal or irrigation fluids.
In addition, in order to compensate for the cool temperature and dryness of the carbon dioxide insufflation gas, an apparatus and method have been developed to control the temperature and humidity of the insufflation gas as it is delivered into the body. Such an apparatus and method are disclosed in commonly assigned U.S. Pat. No. 5,411,474 to Ott et al., the entirety of which is herein incorporated by reference. Nevertheless, there is room for improvement of a heating, hydrating and filtering apparatus for the delivery of insufflation gases.